A critical role for cell polarity in antigen extraction, processing, and presentation by B lymphocytes.

The activation of B lymphocytes in response to external stimuli represents a key step in the adaptive immune response, which is required for the production of high-affinity antibodies and for the generation of long-term memory. Because the dysregulation of B lymphocyte responses can lead to diverse pathological situations, B cells are considered today as valuable therapeutic targets for immunomodulation, in particular in the context of autoimmune reactions. Here, we review the fundamental molecular and cell biological mechanisms that enable B cells to efficiently sense, acquire, and respond to extracellular antigens. A special emphasis is given to cell polarity, which was shown to be critical for the regulation of antigen acquisition, processing, and presentation by B lymphocytes. How cell polarity coordinates the various steps of B lymphocyte activation and might impact the humoral immune response is further discussed.